通过对2G/3G 呼叫测试，分析不同厂商设备主被叫呼叫信令流程，呼叫接续流程耗时，进而优化减少呼叫时 延。在此基础上对4G 网络的CSFB (Circuit Switched Fallback 电路域回落)呼叫时延进一步分析，对网内优化具有一定的参考 价值。

This paper aims to optimize call delay in 2G/3G network by analyzing signaling flow and call-connection time between calling and called parties from different manufacturers. And it further analyzes on CSFB (Circuit Switched Fallback) call delay in 4G network, thus provides network optimization with very important reference value.